1. Field of the Invention
The invention lies in the printing field. Specifically, the invention relates to a device for imprint printing with a rotary printing press.
Rotary printing presses are conventionally used to imprint small area images in otherwise finished stock. It is often necessary to imprint a small area message or image onto a partial batch of product within a larger print job. For instance, it may be necessary to personalize, batch-code, bar-code, or date a given advertising flyer or a packaging cardboard prior to final post-press finishing.
The rotary printing press for imprint printing may be a flexo printer, an offset printer, a letterpress, or a lithographic printer. The product may be processed in a web which is cut and folded subsequent to the final imprint, or it may be processed in sheets. The different machines are referred to as web-fed rotary printing presses and sheet-fed rotary printing presses.
Depending on the number of partial batches into which the complete batch is divided, i.e., depending on how many different imprints are required, it is necessary to stop the press each time and change the imprinter head and, if present, the printing plate. The stoppage and the changeover lead to considerable time losses. Also, the make-ready and the new startup lead to product waste.
2. Description of the Related Art
German patent application No. DE 40 31 964 A1, for instance, describes a rotary printing device with which small area print images are imprinted on a paper web. The device is essentially a web-fed letterpress system with an impression roller carrying the image base body, a counter-pressure roller, an inking roller, and a transport system. The impression roller is formed with an axial groove in which the imprinter head is attached. The imprinter head may be shifted axially in the groove so as to place the imprint image laterally on the product. It is also possible to attach several imprinter heads along the groove. This makes it possible to imprint two or more signatures parallel to each other, or place more than one imprint on the same signature. The inking system includes an ink pan with ink, an ink pickup roller which is partially immersed in the ink, and an inking roller in contact with the pickup roller and the imprinter head. The inking roller thus transfers the ink from the pickup roller to the imprinter head which, in turn, transfers the ink onto the product as it travels through the roller nip between the impression roller and the counterpressure roller.
If it becomes necessary to change the imprint image, the transport system must be stopped and the imprinter head must be changed over to the new image. This causes undesireable stoppage and waste product.
It is accordingly an object of the invention to provide a rotary imprint printing system, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which allows on-the-fly changeover to a new imprint image and, as a result, provides for substantially decreased downtime, reduced product spoilage, and lower overall printing machine cost.
With the foregoing and other objects in view there is provided, in accordance with the invention, a rotary imprint printing system, comprising:
a printing roller having a periphery and an axial channel formed in the periphery;
an imprinter head disposed in the channel, the imprinter head having a print surface substantially parallel with the periphery of the printing roller, the imprinter head being supported in the channel to be radially extendible out of the channel such that the print surface projects radially beyond a plane defined by the periphery of the printing roller.
In accordance with an added feature of the invention, the printing roller has a given axial length and the axial channel extends substantially entirely along the given axial length.
In accordance with an additional feature of the invention, a pressure fluid system is partly disposed in the channel radially below the imprinter head for selectively raising and lowering the imprinter head.
In accordance with another feature of the invention, the pressure fluid system comprises an inflatable member, such as a bladder or a bellows, disposed radially below the imprinter head in the channel, a fluid control device for controlling a selective inflation and deflation of the inflatable member, and fluid lines fluidically connecting the inflatable member with the fluid control device.
In accordance with a further feature of the invention, the imprinter head is one of a plurality of imprinter heads each disposed to individually and selectively project from the periphery of the printing roller, and including a pressure fluid system for selectively raising and lowering each of the plurality of imprinter heads, the pressure fluid system including a plurality of inflatable members each disposed radially below a respective the imprinter head in the channel, a fluid control device for controlling a selective inflation and deflation of each of the plurality of inflatable members, and fluid lines fluidically connecting the inflatable members with the fluid control device.
In accordance with again an added feature of the invention, the imprinter heads are all disposed to axially travel along the axial channel and assume any of a number of defined positions along the axial channel.
In accordance with again an additional feature of the invention, the axial channel has a bottom and sidewalls, the sidewalls having recessed grooves formed therein, and including a carriage supporting the imprinter head axially shiftably within the axial channel along the recessed grooves.
In accordance with again another feature of the invention, the recessed grooves form cam tracks defining a radial position of the carriage, the cam tracks varying a radial location thereof along an axial extent of the axial channel.
In accordance with again a further feature of the invention, the axial channel is divided into three sections along an axial extent thereof and each imprinter head of the plurality of heads is disposed to be selectively transported into any of the three sections.
In accordance with yet another feature of the invention, the sections include a waiting section in which the print heads are disposed in a retracted position prior to an active printing state thereof, a printing section into which each of the imprinter heads is movable from the waiting section and in which the respective printing surface projects axially beyond the periphery of the printing roller, and a discharge section into which the imprinter heads are movable from the printing section.
In accordance with an advantageous feature of the invention, the imprint printing machine is a flexo printer. The print surface is thus a raised printing surface for letterpress printing, and the system includes a counterpressure roller disposed in a nipping relationship with the printing roller and forming a nip adapted to transport a product to be imprinted between the printing roller and the counterpressure roller.
In accordance with a concomitant feature of the invention, system is an offset printing system and the imprinter head carries an offset printing plate defining the print surface.
Three primary advantages that are obtained with the novel system become immediately evident:
1. Eliminate the need for free-standing imprint.
2. Increase productivity with on the run head changes.
3. Reduce overall press purchase price.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a rotary imprint printing system, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of the specific embodiment when read in connection with the accompanying drawings.